samples: bpf: compile and link against full libbpf

samples/bpf currently cherry-picks object files from tools/lib/bpf
to link against.  Just compile the full library and link statically
against it.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

samples/bpf/Makefile

@@ -49,7 +49,7 @@ hostprogs-y += xdpsock
 hostprogs-y += xdp_fwd
 
 # Libbpf dependencies
-LIBBPF := ../../tools/lib/bpf/bpf.o ../../tools/lib/bpf/nlattr.o
+LIBBPF := ../../tools/lib/bpf/libbpf.a
 CGROUP_HELPERS := ../../tools/testing/selftests/bpf/cgroup_helpers.o
 TRACE_HELPERS := ../../tools/testing/selftests/bpf/trace_helpers.o
 
@@ -74,10 +74,10 @@ offwaketime-objs := bpf_load.o $(LIBBPF) offwaketime_user.o $(TRACE_HELPERS)
 spintest-objs := bpf_load.o $(LIBBPF) spintest_user.o $(TRACE_HELPERS)
 map_perf_test-objs := bpf_load.o $(LIBBPF) map_perf_test_user.o
 test_overhead-objs := bpf_load.o $(LIBBPF) test_overhead_user.o
-test_cgrp2_array_pin-objs := $(LIBBPF) test_cgrp2_array_pin.o
-test_cgrp2_attach-objs := $(LIBBPF) test_cgrp2_attach.o
-test_cgrp2_attach2-objs := $(LIBBPF) test_cgrp2_attach2.o $(CGROUP_HELPERS)
-test_cgrp2_sock-objs := $(LIBBPF) test_cgrp2_sock.o
+test_cgrp2_array_pin-objs := test_cgrp2_array_pin.o $(LIBBPF)
+test_cgrp2_attach-objs := test_cgrp2_attach.o $(LIBBPF)
+test_cgrp2_attach2-objs := test_cgrp2_attach2.o $(LIBBPF) $(CGROUP_HELPERS)
+test_cgrp2_sock-objs := test_cgrp2_sock.o $(LIBBPF)
 test_cgrp2_sock2-objs := bpf_load.o $(LIBBPF) test_cgrp2_sock2.o
 xdp1-objs := bpf_load.o $(LIBBPF) xdp1_user.o
 # reuse xdp1 source intentionally
@@ -91,7 +91,7 @@ tc_l2_redirect-objs := bpf_load.o $(LIBBPF) tc_l2_redirect_user.o
 lwt_len_hist-objs := bpf_load.o $(LIBBPF) lwt_len_hist_user.o
 xdp_tx_iptunnel-objs := bpf_load.o $(LIBBPF) xdp_tx_iptunnel_user.o
 test_map_in_map-objs := bpf_load.o $(LIBBPF) test_map_in_map_user.o
-per_socket_stats_example-objs := $(LIBBPF) cookie_uid_helper_example.o
+per_socket_stats_example-objs := cookie_uid_helper_example.o $(LIBBPF)
 xdp_redirect-objs := bpf_load.o $(LIBBPF) xdp_redirect_user.o
 xdp_redirect_map-objs := bpf_load.o $(LIBBPF) xdp_redirect_map_user.o
 xdp_redirect_cpu-objs := bpf_load.o $(LIBBPF) xdp_redirect_cpu_user.o
@@ -165,6 +165,8 @@ HOSTCFLAGS += -I$(srctree)/tools/lib/ -I$(srctree)/tools/include
 HOSTCFLAGS += -I$(srctree)/tools/perf
 
 HOSTCFLAGS_bpf_load.o += -I$(objtree)/usr/include -Wno-unused-variable
+HOSTLOADLIBES_test_lru_dist += -lelf
+HOSTLOADLIBES_sock_example += -lelf
 HOSTLOADLIBES_fds_example += -lelf
 HOSTLOADLIBES_sockex1 += -lelf
 HOSTLOADLIBES_sockex2 += -lelf
@@ -176,6 +178,10 @@ HOSTLOADLIBES_tracex4 += -lelf -lrt
 HOSTLOADLIBES_tracex5 += -lelf
 HOSTLOADLIBES_tracex6 += -lelf
 HOSTLOADLIBES_tracex7 += -lelf
+HOSTLOADLIBES_test_cgrp2_array_pin += -lelf
+HOSTLOADLIBES_test_cgrp2_attach += -lelf
+HOSTLOADLIBES_test_cgrp2_attach2 += -lelf
+HOSTLOADLIBES_test_cgrp2_sock += -lelf
 HOSTLOADLIBES_test_cgrp2_sock2 += -lelf
 HOSTLOADLIBES_load_sock_ops += -lelf
 HOSTLOADLIBES_test_probe_write_user += -lelf
@@ -195,6 +201,7 @@ HOSTLOADLIBES_tc_l2_redirect += -l elf
 HOSTLOADLIBES_lwt_len_hist += -l elf
 HOSTLOADLIBES_xdp_tx_iptunnel += -lelf
 HOSTLOADLIBES_test_map_in_map += -lelf
+HOSTLOADLIBES_per_socket_stats_example += -lelf
 HOSTLOADLIBES_xdp_redirect += -lelf
 HOSTLOADLIBES_xdp_redirect_map += -lelf
 HOSTLOADLIBES_xdp_redirect_cpu += -lelf
@@ -226,7 +233,7 @@ clean:
 	@rm -f *~
 
 $(LIBBPF): FORCE
-	$(MAKE) -C $(dir $@) $(notdir $@)
+	$(MAKE) -C $(dir $@)
 
 $(obj)/syscall_nrs.s:	$(src)/syscall_nrs.c
 	$(call if_changed_dep,cc_s_c)